database - Is a bidirectional relationship appropriate for reference tables? -


please excuse me if stupid question, i'm new @ relational databases , can't seem find answer (probably because else knows answer).

i'm storing test data may include times in various formats different (tai, utc, gps, etc). i'm not sure want force times converted arbitrary consistent format before being input (or maybe that's best way?), assuming can keep flexibility, plan use reference table (lookup table) of time types so:

ref_time_types -------------- id (pk) desc (utc, gps, tai, etc)

and i'll have table store actual times:

tbl_time ------------- id (pk) ref_time_types.id (fk) seconds year . . .

my question i'm sure basic. should establish bidirectional relationship between these, or unidirectional many-to-one tbl_time ref_time_types? can't think of reason want find utc times, example. guiding principle on whether create bidirectional relationship? there best practice when comes relationships reference tables?

i'm using python, sqlalchemy, , sqlite if makes difference.

do need preserve format?

  1. if no, don't store in database. database storing data, shouldn't care how data represented in ui. so, i'd recommend handle input want in ui (if means multiple formats, it), convert consistent format before storing database , rid of ref_time_types altogether.
  2. if yes, go ahead , store format well, i'd still use consistent representation of date/time since require less conversions when querying (you need convert input criteria query, instead of rows don't match desired format).

also, use date/time type supported dbms - don't see particular reason split various date/time components separate fields unless want query on these individual components (and want index them).

should establish bidirectional relationship between these, or unidirectional many-to-one tbl_time ref_time_types?

as discussed above, won't need relationship in first case (since there 1 table). relationship many-to-1 second case.


Comments

Post a Comment

Popular posts from this blog

jquery - Invalid Assignment Left-Hand Side -

i trying assign class tag via jquery, resulting in error through firebug says "invalid assignment left-hand side" on fourth line below. <cfoutput> $('.pngfix a').each(function(index) { var hreflink = $(this).attr("href"); if (hreflink.tolowercase() = '../audio.cfm') { $(this).addclass('audioimg'); } }); </cfoutput> looking around online, looks syntax problem, don't seem see it... any tips? thanks if (hreflink.tolowercase() = '../audio.cfm') that attempts assign value, rather check equality. change = operator == .
Read more

java - Play! framework 2.0: How to display multiple image? -

i need display gallery of photos. here template: @(photos: list[photo]) @title = { <bold>gallery</bold> } @main(title,"photo"){ <ul class="thumbnails"> @for(photo <- photos) { <li class="span3"> <a href="#" class="thumbnail"> <img src="@photo.path" alt=""> </a> </li> } </ul> } and here controller method: public static result getphotos() { return ok(views.html.photo.gallery.render(photo.get())); } and here photo bean : @entity public class photo extends model { @id public long id; @required public string label; public string path; public photo(string path, string label) { this.path = path; this.label = label; } private static finder<long, photo> find = new finder<long, photo>( long.class, photo.class); public static list<phot...
Read more

gmail - Is there any documentation for read-only access to the Google Contacts API? -

i want read-only access user's google contacts. there stackoverflow member wanted this, , received following answer : yes, there is, use https://www.googleapis.com/auth/contacts.readonly scope , "view contacts". this exchange reference read-only access google contacts can find using google. simply using access token obtained attempt read usual google contacts api (i.e. https://www.google.com/m8/feeds ) fails insufficient permissions. similarly, using google contacts api on new target fails 404 errors (for example https://www.googleapis.com/auth/contacts.readonly/default/full ). is there documentation anywhere on how use api, or permissible way access google contacts api full read-write access?
Read more